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<title>Skiers</title>
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<h1>POI VII Stage 1 Problem 3</h1>
<h1>Skiers</h1>
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<p>
 A ski team organizes a training on the Bytemountain. There is one ski
 lift on the northern slope of the mountain. All the ski runs lead from
 the upper ski lift station to the bottom one.
 During the training the team members will start together from the upper
 station and meet at the bottom one. Apart from these two points, the ski
 runs of the competitors cannot intersect, nor adhere to each other. All
 ski runs always have to lead downwards.
</p>

<p>
 A map of ski runs consists of net of clearings connected by 
 glades. Every clearing lies on a different height. Two clearings can be
 joint directly with at most one glade. While skiing downhill from
 the upper to the bottom station of ski lift, one can choose way to visit
 any  clearing (but maybe not all in one downhill run). Ski runs can
 intersect only on the clearings and do not lead through tunnels, or
 flyovers.  
</p>

<h2>Task</h2>
<p>
Write a program, which: 
</p>

<ul>
<li>reads the map of ski runs from the text file NAR.IN, 
<li>determines maximum number of competitors who can participate in training,
<li>write the result to the text file NAR.OUT. 
</ul>

<h2>Input</h2>

<p>
 In the first line of the input file NAR.IN, there is an integer <i>n</i>,
 that equals to the number of the clearings, 2 &lt;= <i>n</i> &lt;= 5 000.
</p>

<p>
 In each of the next <i>n</i>-1 lines there is a sequence of integers separated
 by single spaces. Numbers in the (<i>i</i>+1)-th line describe, to which
 clearings the downhill glades from the <i>i</i>-th clearing lead. First integer
 in the line - <i>k</i> is the number of these clearings, and the following
 <i>k</i> integers are their numbers, which are ordered according to
 the arrangement of glades leading to them, in east to west
 direction. The clearings are numbered from 1 to <i>n</i>. The upper station of
 the ski lift can be found on the clearing number 1 and the bottom one on
 the clearing number <i>n</i>. 
</p>

<h2>Output</h2>

<p>
 The first and the only one line of the output file NAR.OUT should
 consist of exactly one integer - the maximum number of skiers able
 to take part in the training.
</p>

<h2>Sample Input</h2>
<pre>
15
5 3 5 9 2 4 
1 9
2 7 5 
2 6 8 
1 7 
1 10
2 14 11 
2 10 12 
2 13 10
3 13 15 12 
2 14 15
1 15 
1 15 
1 15
</pre>

<h2>Sample Output</h2>
<pre>
3
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